Casualties and battle points

[peppoland]

Hi, I've read this page: http://www.mds.pl/dragon-lords-2-units-and-battle/
but I do not understand how casualties and battle points are really calculated.

On the page is written "Casualties are being calculated basing on attacking units' attack and defenders' defense values. Only defending units suffer casualties in this step. The combined power of all eliminated units is added to attackers' battle points."

For casualties I really do not understand when they happen and how they are calculated starting from units' statistics, and about battle points I obtain strange results. Based on what I read, I aspected that during a clash, if I lose 21 Crushers, my opponent would gain 36 points (21 x 3 that is fair Crusher Power) but in the realm test, this situation seems to give 158 battle points (maybe this is not true, and it's just the effect of the way battles are visualized).

I'm not sure if you can / want to explain math behind this stuff, but I think it would be nice to understand how things works, when playing a math game.
Thanks for your attention and for the nice game that you created.